1. Field of Invention
The present invention relates to telecommunications and, more particularly, to setting up emergency services calls between communication devices and emergency services networks.
2. Description of Related Art
Emergency services calls may be placed for many reasons, such as to request police assistance, to request fire-fighting assistance, or to request emergency medical service. Emergency services calls may be placed by dialing an emergency telephone number. Many countries have established a unique emergency telephone number that may be dialed within their country to place an emergency services call.
In many cases, the emergency telephone number has fewer digits than telephone numbers used to place non-emergency calls. Advantageously, the use of fewer digits allows the emergency telephone number to be dialed more quickly and reduces the burden of having to remember a telephone number having more digits. As examples, the emergency telephone number in Japan is 119, and the emergency telephone number in the United Kingdom is 999. As another example, the emergency telephone number in the United States is 911. In most parts of the United States, both landline telephones and wireless communication devices (WCDs), such as cell phones, may place emergency services calls by dialing the digits 911.
Further, a telephone system that facilitates placing an emergency services call to an emergency telephone number may provide a location of the caller to an agent station that handles the caller's emergency services call. That way, an agent handling the caller's emergency services call can dispatch emergency service providers to the caller's location.
Under current industry standards, when a mobile switching center (MSC) receives a 911 call from a cellular WCD, the MSC will send an IS-41 ORREQ message via a signaling system No. 7 (SS7) network to a mobile positioning center (MPC) to facilitate determination of the calling WCD's location. The MPC will then respond to the MSC with an emergency services routing key (ESRK), which is a key that (i) uniquely identifies an emergency services call in a given cell site/sector, and (ii) correlates data that is provided to an emergency services network (ESN) by different paths, such as a voice path and an automatic location identification (ALI) data path. The MSC will then set up the call over a designated trunk group to a local ESN and provide the ESN with the ESRK. In particular, the MSC will engage in ISUP call setup signaling via the SS7 network with an ESN switch or router, to set up the call and provide the ESRK. The ESN will then use the ESRK to determine the calling WCD's location, typically by querying the MPC over an IP network connection. Further, an automatic call distributor (ACD) of the ESN will set up the call to an available agent station for handling of the emergency services call and will provide the agent with the determined location, to assist the agent in responding to the call.